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 * Copyright (c) 2010, 2017, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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 */

package biz.ganttproject.lib.fx.treetable;

import javafx.event.EventHandler;
import javafx.scene.control.Control;
import javafx.scene.control.IndexedCell;
import javafx.scene.control.ScrollToEvent;
import javafx.scene.control.SkinBase;

/**
 * Parent class to control skins whose contents are virtualized and scrollable.
 * This class handles the interaction with the VirtualFlow class, which is the
 * main class handling the virtualization of the contents of this container.
 *
 * @since 9
 */
public abstract class VirtualContainerBase<C extends Control, I extends IndexedCell> extends SkinBase<C> {

  /* *************************************************************************
   *                                                                         *
   * Private fields                                                          *
   *                                                                         *
   **************************************************************************/

  private boolean itemCountDirty;

  /**
   * The virtualized container which handles the layout and scrolling of
   * all the cells.
   */
  private final VirtualFlow<I> flow;

  private EventHandler<? super ScrollToEvent<Integer>> scrollToEventHandler;


  /* *************************************************************************
   *                                                                         *
   * Constructors                                                            *
   *                                                                         *
   **************************************************************************/

  /**
   *
   * @param control the control
   */
  public VirtualContainerBase(final C control) {
    super(control);
    flow = createVirtualFlow();

    scrollToEventHandler = event -> {
      // Fix for RT-24630: The row count in VirtualFlow was incorrect
      // (normally zero), so the scrollTo call was misbehaving.
      if (itemCountDirty) {
        // update row count before we do a scroll
        updateItemCount();
        itemCountDirty = false;
      }
      flow.scrollToTop(event.getScrollTarget());
    };
    control.addEventHandler(ScrollToEvent.scrollToTopIndex(), scrollToEventHandler);
  }



  /* *************************************************************************
   *                                                                         *
   * Abstract API                                                            *
   *                                                                         *
   **************************************************************************/

  /**
   * Returns the total number of items in this container, including those
   * that are currently hidden because they are out of view.
   * @return the total number of items in this container
   */
  protected abstract int getItemCount();

  /**
   * This method is called when it is possible that the item count has changed (i.e. scrolling has occurred,
   * the control has resized, etc). This method should recalculate the item count and store that for future
   * use by the {@link #getItemCount} method.
   */
  protected abstract void updateItemCount();



  /* *************************************************************************
   *                                                                         *
   * Public API                                                              *
   *                                                                         *
   **************************************************************************/

  /**
   * Create the virtualized container that handles the layout and scrolling of
   * all the cells. This enables skin subclasses to provide
   * a custom {@link VirtualFlow} implementation.
   * If not overridden, this method intantiates a default VirtualFlow instance.
   * @return newly created VirtualFlow instance
   * @since 10
   */
  protected VirtualFlow<I> createVirtualFlow() {
    return new VirtualFlow<>();
  }

  /**
   * {@inheritDoc} <p>
   * Overridden to remove EventHandler.
   */
  @Override
  public void dispose() {
    if (getSkinnable() == null) return;
    getSkinnable().removeEventHandler(ScrollToEvent.scrollToTopIndex(), scrollToEventHandler);
    super.dispose();
  }

  /**
   * Get the virtualized container.
   * Subclasses can invoke this method to get the VirtualFlow instance.
   * @return the virtualized container
   * @since 10
   */
  protected final VirtualFlow<I> getVirtualFlow() {
    return flow;
  }

  /**
   * Call this method to indicate that the item count should be updated on the next pulse.
   */
  protected final void markItemCountDirty() {
    itemCountDirty = true;
  }

  /** {@inheritDoc} */
  @Override protected void layoutChildren(double x, double y, double w, double h) {
    checkState();
  }

  /* *************************************************************************
   *                                                                         *
   * Private methods                                                         *
   *                                                                         *
   **************************************************************************/

  double getMaxCellWidth(int rowsToCount) {
    return snappedLeftInset() + flow.getMaxCellWidth(rowsToCount) + snappedRightInset();
  }

  double getVirtualFlowPreferredHeight(int rows) {
    double height = 1.0;

    for (int i = 0; i < rows && i < getItemCount(); i++) {
      height += flow.getCellLength(i);
    }

    return height + snappedTopInset() + snappedBottomInset();
  }

  void checkState() {
    if (itemCountDirty) {
      updateItemCount();
      itemCountDirty = false;
    }
  }

  void requestRebuildCells() {
    flow.rebuildCells();
  }

}
